1. Field Of The Invention
The present invention relates to an apparatus for processing sewing data utilized by a sewing machine to automatically form an embroidery on a workfabric.
2. Related Art Statement
There is known an apparatus which produces sets of stitch-position data by utilizing a small amount of given information, namely, sets of position data indicative of the coordinates of the vertices of each of the elementary blocks of an embroidery area, and a stitch density, i.e., number of stitches formed in unit length, so that a sewing machine produces an embroidery in the embroidery area by forming stitches at the stitch positions in each of the blocks which positions are indicated by the sets of stitch-position data. An example of the apparatus is disclosed in U.S. Pat. No. 4,388,883.
Regarding a block BK shown in FIG. 6A, the apparatus of the above-indicated type first determines a length of a straight line segment connecting between respective middle points P.sub.a and P.sub.b on sewing start and end sides S.sub.s and S.sub.e of block BK, and subsequently determines a number of stitches formed in block BK, by multiplying the determined length by a given stitch density (i.e., number of stitches per unit length). Further, the apparatus determines stitch positions P.sub.1, P.sub.2, . . . on upper and lower sides S.sub.u and S.sub.l of block BK, by utilizing the determined number of stitches, and produces sets of stitch-position data each of which is indicative of the position of a corresponding one of the determined stitch positions.
In the event, however, that the above apparatus is operated for adjacent three blocks BK.sub.1, BK.sub.2 and BK.sub.3 shown in FIG. 6B, wherein blocks BK.sub.1, BK.sub.2 are a rectangle and block BK.sub.3 is a parallelogram, an "apparent" density of stitches, namely, stitch density perceived by a human being, regarding block BK.sub.2, is higher than that regarding block BK.sub.1 or BK.sub.3 adjacent to block BK.sub.2. In other words, the apparent stitch density in block BK.sub.2 is not uniform with that in block BK.sub.1 or BK.sub.3.
There is known another apparatus which determines, regarding a parallelogram block, the distance between the sewing start and end sides of the block, and determines a number of stitches formed in the block, by utilizing the determined distance. This type of apparatus is disclosed in Publication No. 1-158993 of unexamined Japanese Patent Application filed by the Assignee of the present U.S. patent application.
The above indicated, second apparatus is adapted to deal with a block whose sewing start and end sides are parallel to each other, or a parallelogram or rectangle block. Accordingly, regarding parallelogram block BK.sub.4 and rectangle block BK.sub.6 shown in FIG. 6C, the apparatus determines the distance between the sewing start and end sides of each of the blocks and produces sewing data necessary to form stitches in the each block. Sewing data consist of sets of stitch-position data indicative of the positions of stitches formed on the upper and lower sides of a block which sides are different from the sewing start and end sides of the block. However, regarding block BK.sub.5 of FIG. 6C, the apparatus fails to determine the distance therefor, since block BK.sub.5 is not a parallelogram or rectangle. Thus, in the case of dealing with a block whose sewing start and end sides are not parallel to each other, the second apparatus fails, like the previously indicated first apparatus, to produce sewing data which results in forming stitches in the block such that the apparent stitch density in the block is uniform with that of one or two blocks adjacent to the block. Regarding block BK.sub.5 of FIG. 6C, the second apparatus produces sewing data which results in forming stitches in the block as indicated in two-dot chain line in the figure. As can be seen from FIG. 6C, the apparent stitch density in block BK.sub.5 lacks harmony with that in adjacent parallelogram or rectangle block BK.sub.4 or BK.sub.6.